Process and apparatus for mixing viscous liquids



Feb. 11, 1969 F. wlLDlNG i 3,427,002

PROCESS ND APPARATUS FOR MIXING VISCOUS LIQUIDS Feb. 11, 1969 F. WILDING 3,427,002

PROCESS AND'APPARATUS FOR MIXING VISCOUS LIQUIDS` Filed July'll, 1967 sheet- 2 of 2 United States Patent O 7,079/ 65 U.S. Cl. 259-4 14 Claims Int. Cl. B01f 15/02;F15d 1 00 ABSTRACT F THE DISCLOSURE A mixing apparatus for mixing a stream of viscous liquid or liquids which splits the total flow into a number of sub llows, each of which contains about the same amount of each of the parts to be mixed, and recombines them one at a time.

CROSS REFERENCE TO RELATED APPLICATION This application is a continuation n part of our copending application, Ser. No. 536,509 filed Feb. 18, 1966, and now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the mixing of viscous liquids, that is of liquids of which the viscosity is sufciently high that under practical conditions their flow is laminar and turbulence is absent.

A variety of methods is known for the improvement of uniformity in liquid systems. These can be classified into agitation methods, 4in which a member is moved through the liquid, and streaming methods, in which high speed jets of liquid-s to be mixed are directed together so as to achieve turbulence with consequent intermingling. Of interest in connection with the latter class are United States patent specifications Nos. 2,597,422, 2,788,337 and 3,072,261.

Neither of the classes of methods described is suitable for effecting the mixing of viscous liquids, since with such liquids the requisite high speed of movement of a member through the liquid is impossible, or at least demands a very high expenditure of energy, and the attainment of turbulence is impracticable. These problems are of particular imporatnce where mixing is required of a flowing stream, in which case the time available is limited.

SUMMARY An object of our invention is the improvement of the homogeneity of a plurality of liquids or of a liquid having a plurality of disparate parts.

By the expression improvement of the homegeneity we mean increasing the likelihood that a particular sample portion of the ow taken at random will have the same average composition or other characteristics as any other sample taken at random. In the case of liquids of high viscosity, wherein ow is strictly laminar and turbulence is absent, the improvement in homogeneity will consist in the thinning out of adjacent layers of the liquids, the properties of adjacent layers tending to be dissimilar. Of particular interest is the similarity between the average composition over the Various sections of the crosssection of the combined flow from the apparatus.

By the expression having a plurality of' disparate parts we mean being composed of more than one zone, the zones differing in respect of a secondary characteristic, for example temperature or content of a thermal degradation product rather than in respect of chemical nature.

3,427,002 Patented Feb. 11, 1969 fice The object of our invention is achieved by the splitting of a composite laminar ow comprising a plurality of liquids or a liquid having a plurality of disparate parts into more than two sub-flows or more than two series of su'b-ilows each sub-ow containing approximately the same proportion of each of the liquids or disparate parts of the liquid as any other sub-flow and combining the sub-llows or the series of sub-Hows severally.

By the combining of the sub-ows severally is meant that a sub-flow or series of subflows is added individually to another sub-flow or to a combination of sub-flows. The order of combination is optional. In the case of series of sub-Hows all of the sub-flows of a series will be comlbi1-led simultaneously with another series or combination of series. One or more of the series may consist of one sub-How.

The disposition in the flow of the plurality of liquids or disparate parts of a liquid is preferably arranged to be symmetrical in cross-section in order that the splitting of the sum of the llows into Vsub-flows or series of sub-llows each containing approximately the same proportion of each of the liquids or each of the disparate parts, shall be facilitated. In the case wherein the sum of flows is in the form of skin and core, such splitting of the sum of ilows may be facilitated by attenuating the sum of the flows to form annular flows prior to separation into Subflows. In cases wherein the sum of the flows is side-byside, such splitting of the sum of the flows may be facilitated by attenuating to a thin sheet of flow prior to separation.

We have found that 16 is an adequate number of subflows into which to split the sum of the llows. A greater number of sub-Hows will be no less effective, although presenting increasing practical difliculty as the number increases, and a lesser number may be satisfactory depending on the degree of disparity between the plurality of liquids or parts of a liquid and the perfection of mixing required.

It is preferred to split the sum of the tlows into subflows or series of sub-flows of which each sub-llow carries approximately the same volume of each liquid or disparate parts of a liquid as any other sub-flow or of which each series of sub-flows carries the same volume of each liquid or disparate parts of a liquid as any other series of sub-flows. This can be achieved according to known principles of compensating longer paths by correspondingly wider bores or by arranging to have a greater number of sub-Hows in a series wherein the path is longer.

yConsidering the sub-Hows as numbered consecutively, for example round the perimeter in the case of an annular flow, the order of combination may, for example, be 2 added to l, 3 added to 1+2, 4 added to 1-l-2-i-3 and s0 on, or the order can be staggered, for example, 5 added to 1, 2 added to l-i-S, 6 added to 1+2|5 and so on, or the order may ybe random. In the case of ser-ies of subllows, each member of the series is, of course, combined simultaneously, but each member of the series should be combined with the ow comprising another series or combination of `series at as disparate points as possible.

The point of addition of the sub-flows to another llow may be on the center-line or on the periphery or at any point intermediate between the centre-line and the periphery of the space wherein combination takes place. The various sub-flows may be added at points on a line parallel to the centre-line, otherwise the addition of the sub-flows may, for example, be at different points on the periphery of the cross-section. The space in which combination of the sub-flows is effective may beof such coniiguration, that is of progressively increasing cross-section, that the linear flow is substantially constant throughout the Zone wherein the sub-ows are combined despite the gradually increasing volumetric flow.

The process of our invention is suitable for the mixing of liquids of gradually varying properties throughout their mass, for example of melts handled in the melt-spinning of libre-forming polymers, or for the mixing of more than one liquid. Any or all of the liquids subjected to the mixing treatment may be a solution or a dispersion.

DESCRIPTION OF DRAWINGS FIGURE 1 shows a partially cut-away perspective view of a mixing device having 16 sub-flows.

FIGURE 2 shows a cross-section through the long axis of the mixing device of FIGURE 1 showing the course of the ow of one of the sub-flows.

FIGURE 3 shows a mixing device fabricated from a series of metal washers.

FIGURE 4 shows an end view of the device of FIG- URE 3 from the end distant from the cone.

FIGURE 5 shows a washer with segment removed.

PREFERRED EMBODIMENTS Referring to FIGURE 1, a tube 6 (of internal diameter 0.5 inch) communicates with a passageway delineated by a flared tube 7 and a solid conical body 8; the end of the passageway 10 distant from the tube 6 communi- Cates with sixteen smaller passageways 9 disposed parallel to the axis of the tube 6 the shortest passageway being 5/s inch in length and the length of successive passageways 9 increasing by Ms inch progressively around the periphery. Each of the smaller passageways 9 communi- Cates at its end distant from the passageway 10 with a radial passageway of 1%; of an inch in length .and with circular cross-section of 716 inch diameter, communicating in turn with the central passageway 11 and thence to the exit tube 16. The smaller passageways 9 are each composed of a groove JAG inch deep and /l@ inch wide in the periphery 13 of the inner annulus 17 and in part bounded by a portion of the inner wall of the outer annulus 12. The radial communicating passageways 15 are bored through the inner annulus 17.

In operation, in homogeneous liquid or liquids at 5 are forced through the passageway 10 and a portion of each of the differing portions of the liquid or liquids passes into each of the smaller passageways 9, the liquid from each of the smaller passageways then flows into the central pasageway 11 in succession. The liquid flowing from the tube 16 is found to be substantially homogeneous.

Example 1 In a particular experiment, there was fed to the tube 6 a tlow composed of a core of a liquid of viscosity 3,000 poises under the conditions of operation and in which had been dissolved 0.1% by weight of a blue dyestuff surrounded by an annulus of the liquid containing no dyestuff. The volumetric ows of the dyestuff-containing and colourless liquid were in the ratio 4:21. In order to test the efficiency of improvement of homogeneity produced by the mixing device, the composite flow after passage through the mixing device, was separated into three subflows, two of the sub-ows (hereinafter termed a and d) each being equal to a quarter of the composite flow and taken from diametrically opposite sides of the pipe carrying the composite flow and the third sub-ow being the residue of the composite ow. The residue of the composite flow was further split into two sub-flows (hereinafter termed b and c).

Analysis was carried out of each of the sub-flows, a, b, c and d in order to determine the concentration of dyestuff by weight in the liquid. The results of the analyses were as follows:

Concentration of dyestutfs, Sub-ow: percent by weight 4 Example 2 The mixing used was as described in Example 1 except that the number of passageways 9 was 20 each having a wide of only 1A inch and the lengths of the 20 passageways were as follows. Numbering the passageways consecutively around the periphery from 1 to 20, the first passageway was of 5/8 inch in length and the remainder of the passageways increased in length by 1/16 inch in the following order: 1, 5, 9, 13, 17, 2, 6, 10, 14, 18, 3, 7, 11, 15, 19, 4, 8, 12 16, 20.

The radial passageways were duplicated so that each of the 20 passageways led into 2 radial passageways each of 1/s inch diameter and of 3A inch length.

The effectiveness of the mixing device was tested as described in Example 1 by feeding a composite flow of dyestuff-containing core and colourless annulus and splitting the composite ow after passage through the mixing device into four sub-flows a, b, c and d as described in Example 1. The results of analyses of the four subows were as follows:

Concentration of dyestutf,

Sub-flow: percent by weight a 0.01 b 0.02 c 0.014 d 0.016

Example 3 The mixing device used was described in Example 1 except that the number of passageways 9 was 20 each having a width of only 1A inch and in respect of length the passageways were arranged in 5 series. Numbering the passageways consecutively around the periphery from 1 to 20, the lengths of passageways were as follows:

Numbers 1, 5, 9, 13 and 17 were of 2 inches length. Numbers 3, 7, 11, 15 and 19 were of 1%; inches length. Numbers 4, 8, 12, 16 and 20 were of 1% inches length. Numbers 6, 10 and 18 were of 1% inches length. Numbers 2 and 14 were of @is inch length.

The radial passageways were duplicated so that each of the 20 passageways led into 2 radial passageways each of Ms inch diameter and of inch length.

Calculation based on the flow properties of liquids through pipes shows the quantity of liquid passing per unit time through a passageway of each of the series given hereinbefore is proportional respectively to 1, 1.05, 1.49, 1.64 and 2.76. Thus the quantity of liquid passing per unit time through each of the ve series of passageways is proportional to:

That is, the flow rate through each series was of the same order.

The effectiveness of the mixing device was tested as described in Example 1 by feeding a composite fiow of dyestuff-containing core and colourless annulus and splitting the composite flow after passage through the mixing device into four sub-ows a, b, c and d as described in Example 1. The results of analyses of the four sub-ows were as follows:

Concentration of dyestuif, Sub-flow: percent by weight Example 4 The utility of a mixing device having a lesser number of sub-flows was demonstrated by the use of a mixing device of similar design to that used in Examples 1, 2 and 3 but fabricated from a series of metal washers. Referring to FIGURES 3, 4 and 5, the mixing device was formed from 24 metal washers 17 each in the form of an annulus of outside diameter 35 mm., internal diameter 13 mm. and of thickness 1.6 mm. From each of 16 of the washers there was cut a segment 18 of 45. The 24 washers were assembled face to face -by means of an adhesive to form a pile, as shown in FIGURE 4, the order being:

To the free face of the 1st washer, there was stuck by means of a suitable adhesive the base of a cone of polymethylmethacrylate 19 of 38 mm, base and 32 mm. height. Lengths of plastic coated cable 20 and 21 were stuck onto the assemblage of washers on the periphery parallel to the axis of the assemblage and along the diameter of each entire washer in the vicinity of the ret moved segments respectively. The whole assemblage was forced into a tube 26 of internal diameter 38 mm. thus producing a series of passageways 22 terminating in radial passageways 23 each in turn communicating with a tube 24. -In operation, a composite flow is fed to the mixing device at 2'5, the flow is attenuated as it passes the cone 19 into a sheet flow, split into a series of subows through the passageways 22 and combined severally by passage through the radial passageways 23 into the tube 24.

The effectiveness of the mixing device was tested by feeding at 25 a ow composed of a core of a liquid of viscosity 3,000 poises under the conditions of operation and in which had been dissolved 0.1% by weight of a blue dyestut surrounded by an annulus of the same liquid containing no dyestui. Visual examination of the ow clearly showed it to consist of a blue core surrounded by a-clear annulus. On emergence from the mixing device, the ow appeared to be uniformly blue.

What we claim is:

1. A process for mixing a composite laminar flow of a plurality of liquids, or a liquid having a plurality of disparate parts, comprising the steps of:

splitting a sum of the plurality of liquids, or a sum of the disparate parts, into more than two sub-ows, with each sub-flow containing approximately the same proportion of said liquids or disparate parts as any other sub-flow, and

combining said sub-flows severally.

2. A process according to claim 1 wherein the composite ow consists of a core and annulus or annuli.

3. A process according to claim 1 wherein each of the sub-ows carries approximately the same volume per unit time.

4. A process according to claim 1 wherein the composite flow consists of a core and annulus or annuli and each of the sub-flows carries approximately the same volume per unit time.

5. A process for mixing a composite laminar flow of a plurality of liquids, or a liquid having a plurality of disparate parts, comprising the steps of splitting a sum of the plurality of liquids, or a sum of the disparate parts, into more than two series of sub-flows, with each sub-iow containing approximately the same proportion of said liquids or disparate parts as any other sub-ow, and

combining said series of sub-ows severally.

6. A process according to claim 5 wherein the composite ow consists of la core and annulus or annuli.

7. A process according to claim 5 wherein each of the series of the sub-flows carries approximately the same volume per unit of time.

`8. An apparatus for improving the homogeneity of a composite laminar ow comprising:

inlet means for introducing a composite laminar llow into a passageway where the said composite laminar ow can be split into a plurality of sub-Hows,

more than two channels in communication with said inlet means for receiving said composite laminar flow and for splitting the laminar flow into a plurality of sub-flows, with each sub-flow containing approximately the same proportion of each liquid making up the composite liquid, each of said channels communicating with a common outlet duct, with entry points of the various channels with the common outlet duct being distributed between more than two zones along the length of the common outlet duct, said common outlet duct functioning to receive and to severally combine said plurality of sub-flows from said channels.

9. An apparatus according to claim 8 wherein the relationship between the length, cross-sectional area and perimeter of the various channels is such that a flow of liquid passing through the apparatus from the inlet to the common duct is distributed equally to each channel feeding into each zone of the common duct.

10. The apparatus of claim 8 wherein said passageway is dened by a ared extension of said inlet means and a conical core means having its apex directed towards an inlet tube of said inlet means.

11. The apparatus of claim 8 wherein each of said channels is constructed to receive a distribution of the composite laminar flow which is approximately equal to that of each of the remaining channels.

12. An apparatus for improving the 'homogeneity of a composite laminar ow comprising:

inlet means for introducing a composite laminar flow into a passageway where the said composite laminar flow can be split into a plurality of sub-flows,

more than two series of channels in communication with said inlet means for receiving said composite laminar flow and for splitting the laminar flow into a series of sub-flows, each of said channels communicating wtih a common outlet duct, with entry points of the various channels with the common outlet duct being distributed between more than two zones along the length of the common outlet duct, said common outlet duct functioning to receive and to severally combine said series of sub-flows from said channels.

13. The apparatus of claim 12 wherein said passageway is delined by a ared extension of said inlet means and a conical core means having its apex directed towards an inlet tube of said inlet means.

14. The apparatus of claim 12 wherein each of said series of channels is constructed to receive a distribution of the composite laminar ow which is approximately equal to each of the remaining series of channels.

References Cited UNITED STATES PATENTS 2,597,422 5/ 1952 Wood 259-4 XR 2,788,337 4/ 1957 Preiswerk et al. 259-8 XR 3,072,261 1/1963 Smith 138-42 XR `TOHN M. BELL, Primary Examiner.

U.S. Cl. XR. 13S-42 

